Electromagnetic non-destructive quality testing method, and testing circuit and system therefor

A first-order resistor-inductor (RL) circuit is allowed to alternate a direct-current excitation response and a zero-input response so that a direct-current magnetic field generated by an inductor magnetizing coil changes alternately in magnetic field intensity with a change in magnitude of current. After a testing object is placed in the direct-current magnetic field changing alternately in magnetic field intensity, the testing object is magnetized and also causes a change in inductance of the magnetic field. Whether a change occurs in electromagnetic properties of the testing object can be determined and detected by detecting the inductance change of the magnetizing coil or detecting electrical characteristic change caused by the inductance change of the magnetizing coil, thereby determining whether quality defects such as steel wire cracks and wire breakage in a steel wire rope occur. Alternatively, the properties such as a sectional area or a zinc layer thickness can be analyzed.